Well, according to Microsoft, it was about as widespread as those people who had gone to post on the forum.

A statement provided to Kotaku on the matter reads:

There was a situation yesterday (Sunday) in which less than 200 Halo 4 users were being incorrectly banned from accessing certain parts of the game (not banned from Xbox LIVE as a whole), and we have since resolved the issue. All players accounts impacted are working as normal. For more information, please go to the Halo Waypoint forums here.